Conversion of Kline by Lionel 6-21458 SF Powered A unit

I'd do a small experiment first.  I have discovered that many of the truck mounted motors in K-Line stuff have excessive cogging and will not have good low speed performance with ERR back-EMF cruise boards.  Until they get up to more of a "cruising" speed, the locomotives tend to buck at slow speeds.

A simple test is to take the truck and rotate the wheels.  If you feel excessive "steps" as the motor turns, you'll very likely have pretty poor cruise performance.

maxmn, the motors are not Canon, but are made by Mabuchi. K-Line (and continued during the period Lionel marketed K-Line products) used a low voltage motor, which was indicated on the Lionel parts site when those motors were still available. In other words, the K-Line locos with truck mounted motors as you now have (the Alco FA, S-2, MP-15 and RDC) used less current to move. Which was a problem for many operators using traditional Lionel transformers that had a starting voltage of 6-8 volts: Those locomotives would take off in what is often described as "jack-rabbit" starts. I've never had this problem as I use the Lionel 1033 type transformer which has dual voltage settings to the track. The B-U setting of 0-11 volts is perfect for running these types of K-Line locos.

As a side note, these motors in these K-Line diesels are identical to the motors used in similar types of Lionel locos except the motors used by Lionel are a higher voltage motor so they don't have the jack-rabbit starts. BUT they ARE NOT interchangeable for one small but major difference: The spur gears on the K-Line and Lionel motors have different numbers of gear teeth, as do the gears that directly engage the motor.

As another side note, the earlier incarnation of RMT (when they made the Buddy RDC and S-4... their version of the S-2) while using the same K-Line tooling, also made many improvements. One of which was using a high voltage motor. None of my RMT locos exhibit the same motor "growl" when going around tight 027 curves. In fact the RMT locos are much more smoother running and more speed consistent on tight curves, even with all traction tires in place.

In addition to what gunrunnerjohn suggested above, I might add that if you are looking for smoother running on curves, try removing one or two traction tires. Lionel always puts the traction tires on the same side of the motor truck: The geared wheel side.

K-Line put them all over the place during their years of products. Most frequently they were placed diagonally on each motor truck. Having the traction tires on opposite sides of the motor truck might help pulling on uneven track, but it also contributes to the slow down and "growl" on curves.

Remove the traction tires from the side that does not have the geared wheel. It does reduce pulling power a little bit, but helps reduce the slow down and "growl" noise when going around tight curves... if that indeed is what you are wishing to accomplish by converting it to ERR.

Gunner,

Thanks for the info. I've turned both trucks and there appears to be no steps.  However, it may not pay to update them to ERR.

Brienel,

Based on what you said and since I use a ZW and the MTH 4000 transformers which does not support the low voltage start. It appears that I best not update the engine since the results may not be what I want.

Thank you both for helping me.

@brianel_k-lineguy posted:

As another side note, the earlier incarnation of RMT (when they made the Buddy RDC and S-4... their version of the S-2) while using the same K-Line tooling, also made many improvements. One of which was using a high voltage motor. None of my RMT locos exhibit the same motor "growl" when going around tight 027 curves. In fact the RMT locos are much more smoother running and more speed consistent on tight curves, even with all traction tires in place.

Interesting side note.  The Buddy RDC, at least the one I have, indeed has excessive "cogging" of the motor, and it ran like crap using the ERR Cruise Commander.  I switched to the MiniCommander II since cruise was not an option.